1. Field of the Invention
This invention relates to a water reservoir and, more particularly, to an underground water tank used for fire suppression.
2. Background Art
In fire fighting, the location and quantity of water needed to combat the flames is a paramount consideration. This factor is particularly acute in rural settings where there is no centralized water service. In rural communities where no lakes, ponds, or the like are nearby, the ability to fight fires is limited to the amount of water that can be carded on a truck and pumped from local residential wells. The combination of these two sources can be insufficient for large fires--the tank capacity on the trucks being limited and the residential wells having too meager a discharge rate and pressure. An additional source of water is thus needed in these areas.
One alternative that exists in the prior art is an underground tank which is filled with water. Use of these tanks in fire fighting, however, has been limited because the level of fluid could not be easily determined. This is a severe limitation during fire suppression because the operators could not accurately gauge the time or water remaining before the tank was pumped dry.
In addition to these tanks having a significant weakness for use in fire fighting, they likewise fell short of satisfying insurance regulations to be a viable suction source. The Insurance Services Office ("ISO") is the regulatory agency which evaluates fire departments in establishing their ability to extinguish a fire. The ISO specifically addresses suction supplies in its June 1980 edition of the Fire Suppression Rating Schedule. Section 611.E of this edition states: "Where bays, rivers, canals, streams, ponds, wells, cisterns, or other similar sources are available as suction supply for fire department pumpers, the suction supply shall be considered with respect to its ability, including accessibility, availability during freezing weather, floods, droughts, or other adverse conditions to satisfy the Need Fire Flow (NFF) at test locations." Thus, with a tank or cistern buried beneath the ground to be a viable source of water, there must be an apparatus to verify the amount of water. Without such a means to determine the level of water, the source is considered an adverse condition in an insurance evaluation.
Another part of the ISO requirement for a suction source is accessibility during freezing weather. Underground tanks are subject to becoming inapplicable, especially when filled to a point of overflowing so that water remains above the frost line in the ground. Underground tanks thus could be nonfunctional during the winter months.
ISO evaluations consider these limitations of underground tanks that exist in the prior art. Since forty percent (40%) of an evaluation is based on water supply, homes in rural settings are thus frequently penalized for lack of water suction sources. Underground tanks, because of their limitations, do not reduce or alleviate this negative evaluation.
Accordingly, there is a need in the art for a convenient and reliable method of indicating the level of water in an underground tank or cistern. Likewise, a need also exists to protect such underground water sources from freezing so that these suction sources may be used throughout the year. These tanks also require proper ventilation to prevent tank collapse or rupture during the draining or rapid filling of the tank caused by negative vacuum or excessive pressures, respectively. As such, few buried water supplies are in use because of the unreliability that existed with their use.